HARQ Parameter Management for D2D Links

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Solution Overview

Problem

In mixed cellular and Device-To-Device (D2D) systems, it is challenging to adjust the number of autonomous Hybrid Automatic Repeat Request (HARQ) retransmissions effectively to improve D2D communication efficiency, as existing methods are cell-specific and do not adapt well to varying load conditions.

Innovation Solution

A network node determines the HARQ parameter as a step function of load, increasing or decreasing the number of HARQ attempts based on load thresholds to optimize transmission efficiency, reduce interference, and conserve power.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If cell-specific HARQ retransmission configuration is used, then all devices served by the same cell have the same number of HARQ retransmission attempts, but it is difficult to adjust the number of HARQ retransmissions for specific D2D links to improve communication performance

Engineering Contradiction:

Improveadaptability of HARQ retransmission configurationVSAvoidcomplexity of HARQ parameter management

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies local quality by allowing different UEs to have different HARQ retransmission parameters (mPDSCH, mPDCCH) configured specifically for their D2D communication needs, rather than applying a uniform cell-specific configuration. This enables tailored optimization for each UE's channel conditions and service requirements while maintaining overall system manageability through centralized network control.

Inventive Principle:

Principle #3Local quality

2Reliability

If the number of HARQ retransmissions is increased, then transmission reliability is improved, but power consumption increases and interference to other devices increases

Engineering Contradiction:

Improvereliability of D2D transmissionVSAvoidpower consumption of transmitting device

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent applies parameter changes by dynamically adjusting HARQ-related parameters (mPDSCH, mPDCCH, maxHPNRG) based on observed channel conditions, UE capabilities, and service requirements. The network node modifies these parameters to achieve optimal balance between transmission reliability and power consumption, avoiding excessive retransmissions while ensuring adequate communication quality.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements feedback mechanisms where UEs report channel quality indicators (CQI), channel state information (CSI), and reception status to the network node. The network node uses this feedback to adaptively adjust HARQ retransmission parameters, increasing retransmissions when reliability is insufficient and reducing them when channel conditions are good, thereby optimizing power consumption.

Inventive Principle:

Principle #23Feedback

3Reliability

If the number of HARQ retransmissions is increased, then transmission reliability is improved, but interference to neighboring devices increases

Engineering Contradiction:

Improvereliability of D2D transmissionVSAvoidinterference to neighboring devices

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies local quality by configuring UE-specific HARQ parameters that account for local channel conditions and interference environments. Each UE receives tailored parameter settings (mPDSCH, mPDCCH, maxHPNRG) that optimize its transmission reliability while minimizing interference to neighboring cells, rather than applying a uniform cell-specific configuration.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent applies dynamics by enabling the network node to dynamically adjust HARQ retransmission parameters based on real-time observations of channel conditions, interference levels, and UE performance. This dynamic adaptation allows the system to reduce retransmissions when interference is high, thereby protecting neighboring devices while maintaining reliability when conditions permit.

Inventive Principle:

Principle #15Dynamics

4Loss of time

If autonomous HARQ retransmissions are used without HARQ feedback, then transmission delay is reduced, but transmission efficiency decreases when channel conditions are poor

Engineering Contradiction:

Improvetransmission delayVSAvoidtransmission efficiency

Core Design Contradiction:

Loss of timeVSProductivity

Solution Approach 1:

The patent applies parameter changes by configuring the number of autonomous HARQ retransmissions (mPDSCH, mPDCCH) based on channel conditions and service requirements. When channel conditions are good, fewer retransmissions are configured to minimize delay. When conditions deteriorate, the network increases the retransmission count to maintain efficiency, achieving an optimal balance between delay and productivity.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP3363134B1Method and network node for managing HARQ attempts parameter for d2d links

Publication Date: 2023.12.06 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

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AI summary

A network node (110), a first device (111) and methods therein for managing a HARQ parameter indicating a number of autonomous HARQ transmission attempts to be applied for a transmission on at least one D2D link between the first device (111) and the second device (112) are disclosed. The method comprises determining (A010) a load relating to D2D communication between at least the first and second devices (111, 112). Next, the HARQ parameter is determined (A020) based on the load. Corresponding computer programs and carriers therefor are also disclosed.